Abstract:
This study was aimed at understanding the main abiotic
environmental factors controlling the distribution patterns
of abundance and composition of phytoplankton (size less
than 10 lm) assemblages in the coastal waters of southeastern Cote d’Ivoire. Data were collected during two ^
cruises, in January (low-water period) and October (highwater period) of 2014. A total of 67 species were identified
and assigned to Bacillariophyceae (49%), Cyanophyceae
(21%), Chlorophyceae (13%), Euglenophyceae (10%),
Dinophyceae (4%) and Chrysophyceae (3%). Three biotic
zones (I, IIA and IIB) were distinguishable on a Kohonen
self-organizing map after an unsupervised learning process. The diatom genera Eunotia sp., Navicula sp. and
Actinoptychus senarius are significantly associated with I,
IIA and IIB biotic zones, respectively. A clear seasonal cum
salinity trend was apparent in phytoplankton distribution
patterns. Turbidity and nitrate levels were the main abiotic
factors controlling phytoplankton distribution in I, the
upland tidal regions of the lagoon. In regions along the
lagoon–sea continuum, phosphate and turbidity exert the
most control during the low-water season (IIA), while total
dissolved solids control phytoplankton distribution during
the high-water season (IIB). These are climate-sensitive
parameters whose concentrations depend on prevailing
hydroclimatic processes. Therefore, seasonality can have
important consequences on phytoplankton community
and inadvertently the productivity of these systems.
